scholarly journals Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

2019 ◽  
Vol 12 (6) ◽  
pp. 3417-3434 ◽  
Author(s):  
Nicholas W. Davies ◽  
Cathryn Fox ◽  
Kate Szpek ◽  
Michael I. Cotterell ◽  
Jonathan W. Taylor ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Photoacoustic Spectroscopy ◽  
Strong Dependence ◽  
Single Scattering ◽  
Aerosol Absorption ◽  
Aerosol Mass ◽  
Correction Scheme ◽  
Measurement Biases ◽  
Absorption Photometer ◽  
Absorption Measurements

Abstract. Biases in absorption coefficients measured using a filter-based absorption photometer (Tricolor Absorption Photometer, or TAP) at wavelengths of 467, 528 and 652 nm are evaluated by comparing to measurements made using photoacoustic spectroscopy (PAS). We report comparisons for ambient sampling covering a range of aerosol types including urban, fresh biomass burning and aged biomass burning. Data are also used to evaluate the performance of three different TAP correction schemes. We found that photoacoustic and filter-based measurements were well correlated, but filter-based measurements generally overestimated absorption by up to 45 %. Biases varied with wavelength and depended on the correction scheme applied. Optimal agreement to PAS data was achieved by processing the filter-based measurements using the recently developed correction scheme of Müller et al. (2014), which consistently reduced biases to 0 %–18 % at all wavelengths. The biases were found to be a function of the ratio of organic aerosol mass to light-absorbing carbon mass, although applying the Müller et al. (2014) correction scheme to filter-based absorption measurements reduced the biases and the strength of this correlation significantly. Filter-based absorption measurement biases led to aerosol single-scattering albedos that were biased low by values in the range 0.00–0.07 and absorption Ångström exponents (AAEs) that were in error by ± (0.03–0.54). The discrepancy between the filter-based and PAS absorption measurements is lower than reported in some earlier studies and points to a strong dependence of filter-based measurement accuracy on aerosol source type.

scholarly journals Evaluating biases in filter-based aerosol absorption measurements using photoacoustic spectroscopy

2019 ◽  
Author(s):  
Nicholas W. Davies ◽  
Cathryn Fox ◽  
Kate Szpek ◽  
Michael I. Cotterell ◽  
Jonathan W. Taylor ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Photoacoustic Spectroscopy ◽  
Strong Dependence ◽  
Single Scattering ◽  
Aerosol Absorption ◽  
Aerosol Mass ◽  
Correction Scheme ◽  
Measurement Biases ◽  
Absorption Photometer ◽  
Absorption Measurements

Abstract. Biases in absorption coefficients measured using a filter-based absorption photometer (Tricolor Absorption Photometer, or TAP) at wavelengths of 467, 528 and 652 nm are evaluated by comparing to measurements made using photoacoustic spectroscopy (PAS). We report comparisons for ambient sampling covering a range of aerosol types including urban, fresh biomass burning and aged biomass burning. Data are also used to evaluate the performance of three different TAP correction schemes. We found that photoacoustic and filter-based measurements were well correlated, but filter-based measurements generally overestimated absorption by up to 45 %. Biases varied with wavelength and depended on the correction scheme applied. Optimal agreement to PAS data was achieved by processing the filter-based measurements using the recently developed correction scheme of Müller et al. (2014), which consistently reduced biases to 0–17 % at all wavelengths. The biases were found to be a function of the ratio of organic aerosol mass to light-absorbing carbon mass although applying the Müller et al. (2014) correction scheme to filter-based absorption measurements reduced the biases and the strength of this correlation significantly. Filter-based absorption measurement biases led to aerosol single-scattering albedos that were biased low by up to 0.07 and absorption Ångström exponents (AAE) that were in error by ±0.54. The discrepancy between the filter-based and PAS absorption measurements is lower than reported in some earlier studies, and points to a strong dependence of filter-based measurement accuracy on aerosol source type.

scholarly journals Chemical apportionment of southern African aerosol mass and optical depth

2009 ◽  
Vol 9 (19) ◽  
pp. 7643-7655 ◽  
Author(s):  
B. I. Magi
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Cross Sections ◽  
Southern Africa ◽  
Climate Models ◽  
Critical Role ◽  
Carbonaceous Aerosol ◽  
Aerosol Optical Properties ◽  
Aerosol Absorption ◽  
Aerosol Mass

Abstract. This study characterizes the aerosol over extratropical and tropical southern Africa during the biomass burning season by presenting an aerosol mass apportionment and aerosol optical properties. Carbonaceous aerosol species account for 54% and 83% of the extratropical and tropical aerosol mass, respectively, which is consistent with the fact that the major source of particulate matter in southern Africa is biomass burning. This mass apportionment implies that carbonaceous species in the form of organic carbon (OC) and black carbon (BC) play a critical role in the aerosol optical properties. By combining the in situ measurements of aerosol mass concentrations with concurrent measurements of aerosol optical properties at a wavelength of 550 nm, it is shown that 80–90% of the aerosol scattering is due to carbonaceous aerosol, and the derived mass scattering cross sections (MSC) for OC and BC are 3.9±0.6 m2/g and 1.6±0.2 m2/g, respectively. Derived values of mass absorption cross sections (MAC) for OC and BC are 0.7±0.6 m2/g and 8.2±1.1 m2/g, respectively. The values of MAC imply that ~26% of the aerosol absorption in southern Africa is due to OC, with the remainder due to BC. The results in this study provide important constraints for aerosol properties in a region dominated by biomass burning and should be integrated into climate models to improve aerosol simulations.

scholarly journals Chemical, physical, and optical evolution of biomass burning aerosols: a case study

2011 ◽  
Vol 11 (4) ◽  
pp. 1491-1503 ◽  
Author(s):  
G. Adler ◽  
J. M. Flores ◽  
A. Abo Riziq ◽  
S. Borrmann ◽  
Y. Rudich
Keyword(s):  
Biomass Burning ◽  
Agricultural Waste ◽  
Particle Diameter ◽  
Spectrometric Analysis ◽  
Ambient Aerosols ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Absorption ◽  
Aerosol Mass ◽  
Polycyclic Aromatic ◽  
Aerosol Aging

Abstract. In-situ chemical composition measurements of ambient aerosols have been used for characterizing the evolution of submicron aerosols from a large anthropogenic biomass burning (BB) event in Israel. A high resolution Time of Flight Aerosol Mass Spectrometer (HR-RES-TOF-AMS) was used to follow the chemical evolution of BB aerosols during a night-long, extensive nationwide wood burning event and during the following day. While these types of extensive BB events are not common in this region, burning of agricultural waste is a common practice. The aging process of the BB aerosols was followed through their chemical, physical and optical properties. Mass spectrometric analysis of the aerosol organic component showed that aerosol aging is characterized by shifting from less oxidized fresh BB aerosols to more oxidized aerosols. Evidence for aerosol aging during the day following the BB event was indicated by an increase in the organic mass, its oxidation state, the total aerosol concentration, and a shift in the modal particle diameter. The effective broadband refractive index (EBRI) was derived using a white light optical particle counter (WELAS). The average EBRI for a mixed population of aerosols dominated by open fires was m = 1.53(±0.03) + 0.07i(±0.03), during the smoldering phase of the fires we found the EBRI to be m = 1.54(±0.01) + 0.04i(±0.01) compared to m = 1.49(±0.01) + 0.02i(±0.01) of the aged aerosols during the following day. This change indicates a decrease in the overall aerosol absorption and scattering. Elevated levels of particulate Polycyclic Aromatic Hydrocarbons (PAHs) were detected during the entire event, which suggest possible implications for human health during such extensive event.

scholarly journals Constrained two-stream algorithm for calculating aerosol light absorption coefficient from the Particle Soot Absorption Photometer

2013 ◽  
Vol 6 (6) ◽  
pp. 11093-11144 ◽  
Author(s):  
T. Müller ◽  
A. Virkkula ◽  
J. A. Ogren
Keyword(s):  
Absorption Coefficient ◽  
Single Scattering ◽  
Radiative Transfer Model ◽  
Independent Experiment ◽  
Transfer Model ◽  
Optical Parameters ◽  
Correction Scheme ◽  
Using Data ◽  
Absorption Photometer ◽  
Stream Model

Abstract. We present a new correction scheme for filter-based absorption photometers based on a constrained two-stream (CTS) radiative transfer model and experimental calibrations. The two-stream model was initialized using experimentally accessible optical parameters of the filter. Experimental calibrations were taken from literature and from dedicated experiments for the present manuscript. Uncertainties of the model and calibration experiments are discussed and uncertainties for retrieval of absorption coefficients are derived. For single scattering albedos lower than 0.8, the new CTS method and also other correction schemes suffer from the uncertainty of calibration experiments, with an uncertainty of about 20% in the absorption coefficient. For high single scattering albedos the CTS correction significantly reduces error. At a single scattering albedo of about 0.98 the error can be reduced to 30%, whereas errors using the Bond correction (Bond et al., 1999) are up to 100%. The correction scheme was tested using data from an independent experiment. The tests confirm the modeled performance of the correction scheme when comparing CTS to other established correction methods.

scholarly journals Differences in aerosol absorption Ångström exponents between correction algorithms for particle soot absorption photometer measured on South African Highveld

2014 ◽  
Vol 7 (9) ◽  
pp. 9733-9769
Author(s):  
J. Backman ◽  
A. Virkkula ◽  
V. Vakkari ◽  
J. P. Beukes ◽  
P. Van Zyl ◽  
...  
Keyword(s):  
South African ◽  
Urban Pollution ◽  
Absolute Amount ◽  
Data Set ◽  
Aerosol Absorption ◽  
Remote Sites ◽  
Biomass Burning Aerosol ◽  
The Difference ◽  
Absorption Photometer ◽  
Absorption Measurements

Abstract. Absorption Ångstrom exponents (AAE) calculated from filter-based absorption measurements are often used to give information on the origin of the ambient aerosol, for example to distinguish between urban pollution and biomass burning aerosol. Filter-based absorption measurements are a widely used method and are commonly used at aerosol monitoring stations globally. Several correction algorithms are used to account for the artifacts associated with filter-based absorption techniques. These algorithms are of profound importance when determining the absolute amount of absorption by the aerosol. However, this study shows that there are significant differences between the AAEs calculated from these corrections. The study also shows that the difference between AAEs calculated using different corrections can lead to conflicting conclusions on the type of aerosol for the same data set. In this work the AAEs were calculated from data measured with a three-wavelength Particle Soot Absorption Photometer (PSAP) at Elandsfontein on deployed on the South African Highveld for 23 months. The sample air of the PSAP was diluted to prolong filter change intervals. The dilution-corrected PSAP showed a good agreement with a non-diluted MAAP. Thus, the study also shows that the applicability of the PSAP can be extended to remote sites are not often visited or suffer from high levels of pollution.

scholarly journals Constrained two-stream algorithm for calculating aerosol light absorption coefficient from the Particle Soot Absorption Photometer

2014 ◽  
Vol 7 (12) ◽  
pp. 4049-4070 ◽  
Author(s):  
T. Müller ◽  
A. Virkkula ◽  
J. A. Ogren
Keyword(s):  
Absorption Coefficient ◽  
Single Scattering ◽  
Radiative Transfer Model ◽  
Independent Experiment ◽  
Transfer Model ◽  
Optical Parameters ◽  
Correction Scheme ◽  
Using Data ◽  
Absorption Photometer ◽  
Stream Model

Abstract. We present a new correction scheme for filter-based absorption photometers based on a constrained two-stream (CTS) radiative transfer model and experimental calibrations. The two-stream model was initialized using experimentally accessible optical parameters of the filter. Experimental calibrations were taken from the literature and from dedicated experiments for the present manuscript. Uncertainties in the model and calibration experiments are discussed and uncertainties for retrieval of absorption coefficients are derived. For single-scattering albedos lower than 0.8, the new CTS method and also other correction schemes suffer from the uncertainty in calibration experiments, with an uncertainty of about 20% in the absorption coefficient. For high single-scattering albedos, the CTS correction significantly reduces errors. At a single-scattering albedo of about 0.98 the error can be reduced to 30%, whereas errors using the Bond correction (Bond et al., 1999) are up to 100%. The correction scheme was tested using data from an independent experiment. The tests confirm the modeled performance of the correction scheme when comparing the CTS method to other established correction methods.

scholarly journals Evaluation of biomass burning aerosols in the HadGEM3 climate model with observations from the SAMBBA field campaign

2016 ◽  
Author(s):  
B. T. Johnson ◽  
J. M. Haywood ◽  
J. M. Langridge ◽  
E. Darbyshire ◽  
W. T. Morgan ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Climate Model ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Carbonaceous Aerosol ◽  
Aerosol Mass ◽  
Vertical Distributions ◽  
Biomass Burning Aerosol ◽  
Aerosol Properties

Abstract. We present observations of biomass burning aerosol from the South American Biomass Burning Analysis (SAMBBA) and other measurement campaigns, and use these to evaluate the representation of biomass burning aerosol properties and processes in a state-of-the-art climate model. The evaluation includes detailed comparisons with aircraft and ground data, along with remote sensing observations from MODIS and AERONET. We demonstrate several improvements to aerosol properties following the implementation of the GLOMAP-mode modal aerosol scheme in the HadGEM3 climate model. This predicts the particle size distribution, composition and optical properties, giving increased accuracy in the representation of aerosol properties and physical-chemical processes over the CLASSIC bulk aerosol scheme previously used in HadGEM2. Although both models give similar regional distributions of carbonaceous aerosol mass and Aerosol Optical Depth (AOD), GLOMAP-mode is better able to capture the observed size distribution, single scattering albedo, and Ångström exponent across different tropical biomass burning source regions. Both aerosol schemes overestimate the uptake of water compared to recent observations, CLASSIC more so than GLOMAP-mode, leading to a likely overestimation of aerosol scattering, AOD and single scattering albedo at high relative humidity. Observed aerosol vertical distributions were well captured when biomass burning aerosol emissions were injected uniformly from the surface to 3 km. Finally, good agreement between observed and modelled AOD was gained only after scaling up GFED3 emissions by a factor of 1.6 for CLASSIC and 2.0 for GLOMAP-mode. We attribute this difference in scaling factor mainly to different assumptions for the growth of aerosol mass during ageing via oxidation and condensation of organics.

scholarly journals Development of a Universal Correction Algorithm for Filter-Based Absorption Photometers

2019 ◽  
Author(s):  
Hanyang Li ◽  
Gavin R. McMeeking ◽  
Andrew A. May
Keyword(s):  
Great Plains ◽  
Biomass Burning ◽  
Light Transmission ◽  
Reference Value ◽  
Single Scattering ◽  
Department Of Energy ◽  
Monitoring Networks ◽  
Correction Algorithm ◽  
Ambient Aerosols ◽  
Absorption Photometer

Abstract. Among the various measurement approaches to quantify light absorption coefficient (Babs), filter-based absorption photometers are dominant in monitoring networks around the globe. Numerous correction algorithms have been introduced to minimize the artifacts due to the presence of the filter in these instruments. However, from our recent studies conducted during the Fire Influence on Regional and Global Environments Experiment (FIREX) laboratory campaign, corrected filter-based Babs remains biased high by roughly a factor of 2.5 when compared to a reference value using a photoacoustic instrument for biomass burning emissions. Similar over-estimations of Babs from filter-based instruments exist when implementing the algorithms on six months of ambient data from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) user facility from 2013 (factor of roughly 3). In both datasets, we observed an apparent dependency on single scattering albedo (SSA) and absorption Ångström exponent (AAE) in the agreement between Babs based on existing correction factors and the reference Babs. Consequently, we developed a new correction approach that is applicable to any filter-based absorption photometer that includes light transmission from the filter-based instrument as well as the derived AAE and SSA. For the FIREX and SGP datasets, our algorithm results in good agreement between all corrected filter-based Babs values from different filter-based instruments and the reference (slopes ≈ 1 and R2 ≈ 0.98 for biomass burning aerosols and slopes ≈ 1.05 and R2 ≈ 0.65 for ambient aerosols). Moreover, for both the corrected Babs and the derived optical properties (SSA and AAE), our new algorithms work better or at least as well as the two common PSAP-based correction algorithms. The uncertainty of the new correction algorithm is estimated to be ~10 %, considering the measurement uncertainties of the operated instruments. Therefore, our correction algorithm is universally applicable to any filter-based absorption photometer and has the potential to “standardize” reported results across any filter-based instrument.

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